1. Field of the Invention
The present invention generally relates to insulated structural building panels and, more particularly, to advances in the design of the building panels enabling significantly reduced costs of manufacturing the panels and of constructing buildings using the panels.
2. Background of the Invention
Insulated building panels having both structural and insulating properties have long been available in several forms. Among the better known types are structural insulated panels (“SIP”), which typically comprise a solid core of insulating material, such as expanded polystyrene (“EPS”), sandwiched between and bonded to a relatively thin, rigid panel of wood or a laminated material, such as oriented strand board (“OSB”) to provide the needed structural strength to support the various types of loads encountered in a finished building. Other types of insulated building panels rely on metal framing members to provide the needed structural properties. The combination of metal framing members and the EPS core provides improved durability, resistance to insects and the effects of moist environments, in addition to their insulating properties.
Conventional building panels fabricated of expanded polystyrene (EPS) foam and steel framing members (“foam/steel panels”) can provide wall panels for one and two story buildings having excellent insulating properties. The steel framing members or “studs” that are incorporated in these conventional building panels provide structural strength and stability, as well as resistance to insect damage and the effects of moist climates. The combination of the steel framing members and the EPS foam in the conventional building panels provides a relatively light weight panel that is easily handled and erected at a building site. However, the conventional foam/steel building panels are characterized by several significant inefficiencies in the manufacture of the panels and the construction of buildings that results in relatively high costs as compared to ordinary wood frame “stick built” construction.
For example, in FIG. 1A, there is illustrated a cross section one example of a prior art insulated building panel 10 wherein the steel stud members 12 are secured in the foam body 14 of the building panel using a heat activated adhesive 16 applied to the stud members 12 prior to molding the panel. As shown in FIG. 1A, the heat activated adhesive 16, shown as the dashed lines, may be applied to the inside surface of the channel-shaped stud members 12 prior to molding the panel. The stud members 12, typically formed of 24 gauge, galvanized steel, are approximately the same dimensions as wood framing studs. During molding, the heat from the expanding polystyrene foam activates the adhesive 16, bonding the inside surface of the stud members 12 to the foam material 14. Applying the adhesive 16 is a distinct manufacturing step involving its own tooling, set-up and material costs. This prior art example is typically available in widths having standard sixteen inch or twenty-four inch on-center (“O.C.”) spacing. In some examples, complex ship lap joints (not shown) are utilized along the panel edges to provide both a sturdy joint and a thermal break. Other panel sizes may be custom ordered, generally at higher costs to cover the tooling, set-up, and the like.
In FIG. 1B, there is illustrated a cross section of another example of a prior art insulated building panel 20 wherein the steel stud members 22 are secured in the foam body 24 of the building panel 20 using mechanical fasteners 26 between opposing pairs of stud members 22. In this configuration, the steel stud members 22 are a box section member, formed of 18 gauge steel and have dimensions of approximately 1″×2″ in cross section. The studs 22, on 24 inch spacings, are assembled in grooves routed in the surface of the foam panel 24 on opposite sides of the panel 24. Each one of a pair of stud members 22 is secured to the opposite stud member 22 with a screw fastener 26 that passes through the foam material 24, connecting the stud members 22 together. As in the previous example, this prior art example requires a distinct manufacturing step involving additional tooling, set-up and material costs. Moreover, this design lacks a thermal break between each pair of metal studs.
Because of their construction, conventional foam/steel panels are typically available in limited standard sizes and configurations in order to minimize manufacturing costs. Inefficiencies further result from the methods employed to secure the steel framing members to the EPS foam body of the panels. Moreover, since most buildings are generally different from each other in many respects, the standard panels must be cut to size or shape to fit a particular application, which is a labor-intensive and expensive task if conventional tools are used. Alternatively, the panel parts may be prefabricated at the place of manufacture to submitted detail drawings, which is also time consuming and expensive, and generally involves costly tooling and set-up charges. The effect of all of these cost factors substantially limits the marketability of these highly thermal efficient building panels for all but uncomplicated, standardized structures.
What is needed is a foam/steel panel design and component system that enables substantial economies of manufacture and on-site assembly during the construction of buildings such that the use of the foam/steel insulated building panels is at least cost competitive with wood framing and other types of building construction.